The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Semiconductor processing systems may include components that need to be made of silicon (Si) or silicon carbide (SiC). Large components that are made using silicon or silicon carbide are expensive to manufacture. The cost to produce starting blanks for manufacturing these large components increases with finished part dimensions. When using silicon, the starting blanks are typically made from single crystal, dislocation free (DF) silicon ingots and multi-crystalline silicon ingots that are sliced to a required thickness.
In many cases, the machining process is time consuming and has high labor cost. Some components may require large amounts of material to be removed from the starting blank. Some components (such as a gas distribution plate with an internal plenum) are impossible to make using a monolithic silicon blank. Core drilling and electrical discharge machining (EDM) are effective approaches for reducing material loss and machining time for certain types of components such as ring-shaped components. Larger components can be assembled using two or more smaller components that are machined separately and then bonded together. This approach can significantly lower manufacturing costs as compared to machining the equivalent part from a single, monolithic blank.
Elastomers have been used to bond silicon to silicon, silicon to graphite, and silicon to aluminum. However, the elastomer bond has relatively weak tensile strength (typically about ˜470 psi). The use of elastomer also limits the working temperature to about 185° C. The elastomer bond typically has higher resistivity and lower thermal conductivity than bulk silicon. The elastomer bond is also prone to generate particle contamination in substrate processing systems.
Liquid phase bonding involves arranging a bonding agent such as aluminum or gold between the two or more parts to be bonded together. The bonding agent is heated above its melting temperature. While the bonds are typically strong, the maximum application temperature is limited by the eutectic temperature of Si and the bonding agent, which is 580° C. for Si—Al and 363° C. for Si—Au, which may be too low for some substrate processing system applications. Additionally, the bonding agent may increase metallic contamination and generate non-volatile particles during subsequent use in substrate processing systems. In addition to contamination risk, coefficient of thermal expansion (CTE) between Si and the bond materials is typically different which can cause shear stress in Si and weaken the bonded part mechanical strength.